This invention relates to vehicle suspension systems and more particularly, to those suspension systems which are normally employed on large dumping trucks and trailers which are utilized to transport heavy loads of loose materials. The vehicles usually include a large elevatable box, bin, or bed within or on which the materials to be transported are placed and a pivoted tailgate which will permit the materials to be discharged from the rear when the box, bin, or bed is elevated.
As the size, and thus the load carrying capability, of dumping trucks and trailers has increased, so has the incidence of damage caused by such truck or trailer bodies tipping over as a result of elevating the dumping box on terrain which is irregular.
It has been recognized that if a large dump truck or trailer is elevated from the transporting to the dumping position with the wheels of the vehicle and their attendant suspension components in other than a substantially level condition, the tendency is to aggravate the out of plumb condition because of the increased height attained by the elevation of the dumping box. Thus, as the dumping box is raised, the forces of gravity tend to force the load to the low side and if the out of level condition is of sufficient magnitude and the load is raised to a point where the center of gravity is sufficiently out of line with the central axis of the vehicle, the truck will tip over, thus causing loss of both load and vehicle with potential substantial damage to the vehicle and injury to the operator.
It has further been recognized that even if the elevation of the load on out of level terrain is insufficient to cause a vehicle to tip over, it may nonetheless result in a twisting force being applied to the vehicle frame sufficient to "rack" the frame out of square and permanently damage the vehicle components.
In order to reduce the incidence of tipping of dumping truck and trailer vehicles of the type contemplated in this application, I have determined that if the angle of deviation of the elevated load body from a vertical axis can be maintained within predetermined acceptable parameters, the loads may be elevated and dumped without damage to the vehicle and without danger of operator injury.